Mojave toxin from Crotalus scutulatus scutulatus (Mojave rattlesnake) and related toxins from other rattlesnake species will be conjugated to monoclonal antibodies and evaluated for use as an immunotoxin. The holotoxins and the basic subunits will be conjugated to OKT1 antibodies directed against human T cells. The T cell killing activity of the immunotoxin will be evaluated by inhibition of mitogenesis by PHA of cultured human blood lymphocytes. Inhibition of cytotoxic activity of T cells will be done as a confirmation of immunotoxin activity.